Assessment of antiherpetic activity of nonsulfated and sulfated polysaccharides from Azadirachta indica.

Azadirachta indica leaf is used by Indian population for the healing of various diseases including viral infection. Herein, we analyzed the antiherpetic (HSV-1) activity of two polysaccharides (P1 and P2) isolated from the leaf of A. indica and their chemically sulfated derivatives (P1S and P2S). The molecular weights of P1S and P2S are 41 and 11 kDa, respectively. Sulfate groups are located at positions C3 of the Araf and C6 of both Galp and Glcp residues of the most active polysaccharide (P1S). These compounds were not cytotoxic in HEp-2 cells, up to 1000 µg/mL. Both P1S and P2S exhibited antiviral activity when used simultaneously to HSV-1, with 50% inhibitory concentration/selectivity index, respectively, of 31.1 µg/mL/>51.4 and 80.5 µg/mL/>19.8. P1S showed better inhibitory effect (91.8%) compared to P1 (50%), P2 (71.1%) and P2S (70%) at 200 µg/mL. Synthesis of viral protein showed a dose-dependent response and the nucleic acid synthesis was inhibited up to 25 µg/mL, by P1 and P1S and up to 50 µg/mL, by P2 and P2S. The antiviral effect is probably due to the interference of polysaccharides at the early stages of HSV-1 replication, including adsorption. Further studies are under way to get insight into the mechanism of action of the substances.

Green seaweed Enteromorpha compressa (Chlorophyta, Ulvaceae) derived sulphated polysaccharides inhibit herpes simplex virus.

The herpes simplex virus (HSV) diseases represent a relevant medical and social problem due to their communicability and recurrence following latency. The green algae are rich source of polysaccharides referred to as ulvans, reported as being biologically and pharmacologically active. In this work, we analyzed the activity of seven chemically modified polysaccharides from Enteromorpha compressa (Chlorophyta, Ulvaceae), against HSV. Only the derivative named SU1F1 showed satisfactory viral inhibition activity, with a high selectivity index, and, therefore, it was submitted to analysis of the probable mechanism of action and structure. SU1F1 is a sulphated (22% w/w) heteroglycuronan with an apparent molecular mass of 34kDa. The antiviral activity was assayed by plaque reduction assay under the protocols of the time-of-addition (from 3h before infection to 16h after infection), the inhibition of virus adsorption and penetration, and the virucidal effects. SU1F1 showed a high viral activity at the time 0h. We demonstrated that its inhibitory effect was maintained until 4h post-treatment with 100% of viral inhibition at 100µg/ml. No effect was observed in additional protocols (the pre-treatment, the inhibition of adsorption and penetration and virucidal assays). Reverse Transcriptase associated PCR (RT-PCR) results were in accordance with plaque reduction assay and demonstrated the activity of SU1F1 at the initial stages of HSV replication.

Sulfated polysaccharide of Caesalpinia ferrea inhibits herpes simplex virus and poliovirus.

Herpes simplex virus (HSV) is one of the most regular human pathogens, being a public health problem, and causal agent of several diseases. Poliovirus (PV) is an enteric virus and about 1% of infected individuals develop paralytic poliomyelitis due to viral invasion of the central nervous system and destruction of motor neurons. This work evaluated the activity of a sulfated polysaccharide of Caesalpinia ferrea (SPLCf) in HSV and PV replication. The antiviral effect of SPLCf at varying concentrations was tested by plaque assay under several protocols, such as time-of-addition, adsorption and penetration inhibition and virucidal. Syntheses of viral protein and nucleic acid were also monitored by the immunofluorescence assay and PCR. The SPLCf inhibited virus adsorption and steps after penetration, and inhibited the synthesis of viral protein. Virucidal effect was also shown and nucleic acid synthesis was concurrent with positive results. Our findings suggested that the substance with low toxicity represent a potential viral inhibitor.